为避免永磁体局部失磁对永磁电机（PMSM）控制精度和安全运行带来影响，提出了一种基于反电动势（EMF）谐波分析的分数槽集中绕组永磁同步电机（FSCW-PMSM）局部失磁故障诊断方法。在推导出的FSCW-PMSM局部失磁时磁动势（MMF）和单槽反电动势的数学模型基础上，根据单槽反电动势各谐波分量的幅值和特征绕组系数得到单相反电动势各谐波幅值的定量变化关系，并验证利用单相反电动势谐波变化诊断失磁故障的可行性。最后，基于一台20极24槽内置式永磁同步电机的样机参数建立二维有限元模型开展电磁仿真分析，获得单相反电动势特征谐波的变化规律。结果表明单相反电动势特征谐波的大小随故障数量增大呈周期性变化。

To avoid the influence of partial demagnetization of permanent magnet on the control accuracy and safe operation of permanent magnet synchronous motors (PMSMs), a method to monitor partial demagnetization faults for fractional slot concentrated winding (FSCW) PMSM based on back electromotive force (EMF) harmonic analysis is proposed. After theoretical derivation, the mathematical models of magneto motive force (MMF) and single-slot back EMF under demagnetization are obtained. Then, with the amplitude of each harmonic component of the single-slot back EMF and winding coefficients of FSCW-PMSM, the variation of each harmonic amplitude of the single-phase back EMF can be deduced. The theoretical derivation above can verify the feasibility of judging the demagnetization fault by the variation of single-phase back EMF′s harmonics. Finally, using the prototype parameters, taking a 20-pole 24-slot interior PMSM to build a finite element model, a 2D electromagnetic simulation model is established to obtain the variation of the characteristic harmonics of the single-phase back EMF. The results show that the characteristic harmonic of single-phase back EMF changes periodically with the increase of the number of faults.